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Modified Tech Discussion Forum for Tech related discussion for Modified XJ's and MJ's.

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  #1  
Old June 18th, 2003, 23:19
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Low oil pressure warning system and oil pressure back up Q's

Still trying to find out why my cam bearings failed in less than 30K miles. My engine guy called yesterday and said the mains looked good with "only mild wear". Now this is an engine that went 180K before with only "mild wear" so I am going to do new rod and mains since the motor is on the stand.

One of the possibilities I have been tossing around is a transient loss of oil pressure while on steep climbs (Mickey's Hot tub comes to mind). I watch the oil gauge as close as one can while staring at a spotter or the sky but cannot say I have not vented the oil pick up for a short time.

I would like to piggyback a light similar to the tach shift lights and a buzzer of some sort to come on at about 15 PSI or so. Has any one done this and retained the factory pressure gauge too?

In addition, is any one running one of the pressurized oil accumulation systems that are made to keep pressure up for a short time when the pump pickup vents? What is involved in hooking one up on a XJ?


Thanks,

Bones
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Old June 18th, 2003, 23:33
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I used to run a warning light in my race car. That part is simple -- you just put a tee fitting in where the pressure sender is, and use two senders. Use the OEM one for your gauge, and get an OEM idiot light sender to go with it. The one for the idiot light is just an ON/OFF switch that completes a circuit to ground. You can use it to run any kind of light and/or buzzer you want.

One of my racer pals back then did use an oil pressure accumulator tank. His concern was cornering forces cavitating the oil puckup, but the effect is the same as inclines. He ran it on an AMC V-8. I believe to install it he had to put an adapter on the stock oil filter location and set up an external remote filter, which was plumbed in series with the accumulator. To do it on an XJ 4.0L, I think you'd probably remove the stock filter adapter and put the remote adapter right on the block (no point in mounting one adapter on another adapter), then you have to find enough space for both the tank and a remote filter.

You did say you have the battery in the rear, right?
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Old June 19th, 2003, 01:25
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How big are these tanks? I know there are various sizes but a general description would be nice. Summit lists both a 3 qt and a 1.5 qt. Are there any other brands other than Moroso's? What is the flow rate (reserve time) of a 3 qt system given good normal oil pressure. Would running an additive (like Lucas) be anywhere near as good if the pressure drop is very short?

Here is a write-up Cappa did on an accumulator install.
http://www.4wheeloffroad.com/howto/3282/

Looks like it would run about $350-400 plus lines to do this thing right. That figures the accumulator, the 12 volt solenoid, low pressure light and an oil cooler and adapter combo (since the adapter is going in anyway might as well go with the cooler too). Im going to have to do some thinking about this before dropping that much change.

Bones
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Old June 19th, 2003, 06:41
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Bones, racersauction.com and racerjunk.com are good sites for finding parts like this on the cheap. I'm not so sure this is gonna help out too much though for the expense and time. We use the 3 qt. on our formula and at WOT we are looking at 10-15 seconds for reserve. Idle-2000 might net you just over 30 seconds. Oh yeah, the 3 quart is appx. 1.5' long and 4-5" diameter.

Sean
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Old June 19th, 2003, 17:57
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Thanks Sean, I'll check into it.

Another Q:
How much oil can a 4.0 stock pan hold without causing problems at start up. I'm assuming it could hold the extra 3 qts but thought Id check.

Bones
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Old June 19th, 2003, 18:25
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Just curious, what brand/type of oil have you been running ??
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Old June 19th, 2003, 18:35
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Only 10/30W Valvoline SynPower or Mobil 1 since break in.

Bones
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Old June 19th, 2003, 20:31
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Steve,

Something to check into is.... whether there is a restrictor in the path that supplies the oil to the cam bearings. The restrictor might be too small not allowing sufficient oil. Something else to look into would be having a set of baffles brazed in the bottom of the oil pan so that the oil pump pickup does not suck up air when off camber or on extreme upward or downward angles.
On the car that I used to race years ago.... I had a baffle brazed in for a continued oil source during hard acceleration. Worked very well.
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